180 Mr. TV. Peile on a Transformation of Coal. 



the immediate vicinity of a large Slip Dyke, and follows the same course, 

 but it differs from them in having passed through the Seam without 

 branching out on either side, and thus being the same in the Coal as the 

 Riders are in the Stone. May we not infer from this, that the formation 

 of this Stone Dyke was posterior to the consolidation of the Coal, and 

 that the Riders were formed while the substance of the Coal was yet 

 soft ? 



The most natural way of accounting for these Stone Dykes or Riders 

 would be, that a chink or rent of the strata, caused by the convulsion 

 of the large Slip Dyke, had been afterwards filled up by infiltration. 

 The Stone is a hard, fine grained, white Sandstone. 



In the Whitehaven Colliery, large Slip Dykes are very numerous, 

 and cause great expense and difficulty. They offer, however, an ex- 

 cellent opportunity for an examination of their nature and leading 

 features. 



It has been well said by Mr. Buddle, that the substance interposed 

 between the cheeks of a Dyke appears to have been formed by their 

 abrasion. It is generally a fine Clay, called by our miners " the stick- 

 ing," and its fineness and thickness are our index of the extent of the 

 Dyke. In a Dyke that we have lately passed, the " sticking" was three 

 feet thick, of a very fine Clay, and containing imbedded, some pieces of 

 Metal and Sandstone, rounded by abrasion. This Dyke haded from the 

 perpendicular at an angle of 54°, which is very great, and is another 

 index of the extent of throw, but not a very certain one, although 

 generally large Dykes have a great hade. 



